MXPA97005307A - Procedure for the obtaining of rent-ter, butileteres and di-n-buteno from butanos deca - Google Patents

Abstract

The present invention relates to a process for the preparation of di-n-butene and alkyl-butyl ethers in a coupled production from field butanes, in which (a) the butanes of field 1 are separated in the stage of separation 4 in n-butane to iso-butane, (b) in a dehydrogenation step 6 the n-butene 5 is dehydrogenated to a mixture of oligomers 11 and di-n-butene 12 is separated from it, and (c) in the dehydrogenation step 16, the isobutane 15 is dehydrogenated to a dehydrogenation mixture 17 containing n-butene and the iso-butene in the etherification step 19 is transformed with an alkanol 20 to an alkyl tertiary butyl ether 21. The advantageous embodiment is characterized in that the field butanes 1, before entering the separation step 4, in the hydrogenation stage 2 are subjected to hydrogenation conditions and the separation stage 4 is assigned an isomerization stage 3, by means of the which adjusts the amount ratio of n-butane and iso- butane according to the proportion of desired quantities of alkyl-butyl ether to di-n-bute

Description

PROCEDURE FOR THE OBTAINING OF RENT-TER.BUTILÉTERES AND DI-N-BUTENO FROM FIELD BUTANES The invention relates to a process for the preparation of alkyl tertiary butyl ether (hereinafter abbreviated RTBE, where R represents alkyl) and di-n-butene in a production coupled from field butanes, transforming the iso -butane in alkyl-tert.buter and n-butane in di-n-butene and being able to regulate the proportion of quantities of these two products, adjusting correspondingly the amount ratio of n-butane to iso-butane by isomerization. The RTBE are used as an additive for gasoline to increase the octane rating. They are obtained by the addition of alkanols in iso-butene, which is also called etherification. Iso-butene can come from four different sources: thermal vapor decomposers, propylene oxide installations, petroleum refineries (ie, FC decomposers) and facilities for the dehydrogenation of iso-butane (see RA Pogliano et al., Dehydrogenation -Based Ether Production Adding Valué to LPG and Gas Condensate, 1996 Petrochemical Review, DeWitt &Company, Houston Texas). In the case of the first three sources, iso-butene is produced as a component of the C4 cut, that is, as a direct secondary product. In the case of the dehydrogenation of iso-butane, iso-butene is often an indirect by-product of such facilities, since the starting material, isobutane, is also obtained as a direct by-product in thermal steam decomposers and petroleum refineries or by the isomerization of n-butane, which, in turn, is a secondary product in thermal vapor decomposers and petroleum refineries. The current global production of RTBE is approximately 25 million t / year, with an upward trend. The production of butanes and butenes as by-products in a given decomposer or a certain oil refinery is too small to fully take advantage of the "Economies of Scale" that exist in the RTBE procedure. Isobutene and / or iso-butane (for dehydrogenated) of the decomposers and / or refineries would have to be collected in order to operate an RTBE installation with optimum capacity. Alternatively, a sufficient cut of C4 could be collected from these facilities and processed at the site to obtain iso-butene and iso-butane. Both variants, and particularly the second, have the objection that the transport of liquefied gases is very expensive, not ultimately due to the expensive security measures. The isomeric mixture which is formed, in addition to higher oligomers of butene, by the dimerization and / or co-dimerization of butenes, that is, of n-butene and / or iso-butene, in the oligomerization of butenes is referred to as dibutene. Di-n-butene is referred to as the product of the dimerization of n-butene, ie, 1-butene and / or 2-butene. The basic components of di-n-butene are 3-methyl-2-heptene, 3,4-dimethyl-2-hexene and, to a lesser extent, n-octenes. Di-iso-butene is the isomeric mixture obtained by the dimerization of isobutene. Di-iso-butene is more branched than dibutene, and this, in turn, is more branched than di-n-butene. Dibutene, di-n-butene and di-isobutene are starting materials for the preparation of isomeric nonanols by hydroformylation and hydrogenation of the Cg aldehydes obtained in this way. The esters of these nonanoles, particularly the phthalic acid ester, are softeners that are produced in significant volumes and are used mainly for polyvinyl chloride. The di-n-butene nonanoles are, to a greater extent, straight chain than the nanoanes of dibutene, which, in turn, are less branched than the nonanoles of di-iso-butene. The esters of the di-n-butene nonanoles have advantages of technical application with respect to the esters of other nonanoles and, for that reason, they are particularly demanded. N-butene is obtained for the dimerization, as well as iso-butene, for example from cuts of C4, as produced in thermal steam decomposers or FC decomposers. Cuts of C4 are usually processed by first dissociating 1,3-butadiene by selective washing, for example with N-methylpyrrolidone. Iso-butene is a desired and particularly valuable component of C4 cutting, because, alone or mixed with other C4 hydrocarbons, it can be chemically transformed to desired products, for example with iso-butane to high octane iso-octane or with methanol to methyl-tertiary butyl ether (MTBE), the most important RTBE. After the reaction of the iso-butene, the n-butenes and n-butane remain. The part of n-butene in the products of the dissociation of the steam thermal decomposer, or else of the oil refinery, is, however, proportionally low. In the steam thermal decomposers it is around 10% by weight, based on the main target product, ethylene. A steam thermal decomposer with the respectable capacity of 600,000 t / year of ethylene therefore provides only about 60,000 t / year of n-butene. It could increase its amount (and that of the iso-butenes), dehydrogenating about 15'000 t / year of n- and iso-butane, which are produced in addition to the n-butenes. However, it is not recommended, since dehydrogenation facilities require high investment costs and, for such a small capacity, they are not profitable. As it was said, iso-butene is a product of decomposition with great demand and, for this reason, it is usually not available for isomerization to n-butene. The amount of n-butenes produced directly by a steam thermal decomposer or an oil refinery is not enough to produce enough di-n-butene for a nonanol facility, whose capacity is so large that it could compete economically with the large existing facilities for the production of important softening alcohols, such as 2-ethylhexanol. As already mentioned, propylene oxide installations are less productive. Therefore, n-butenes should be collected from various steam thermal decomposers, refineries or propylene oxide installations (or process the cutting of C4 from various sources to n-butene) and oligomerize the pooled n-butene, to cover the need to draw us from a sufficiently large industrial nonanol facility. The transport of liquefied gases, however, is expensive, as already mentioned. Therefore, it would be desirable to be able to make n-butene and iso-butene available in one place without transport over long distances, in the quantities required in a coupled production for the operation of a large, economically advantageous facility, for the production of di-n-butene, for example with a capacity of 200'000 to 800'000 t / year, and another equal facility for the production of MTBE, for example with a capacity of 300'000 to 800'000 t / year. It would also be desirable to configure the mixture of these facilities so that the proportion of n-butene to iso-butene can be adjusted correspondingly to the desired amounts of di-n-butene and MTBE. An installation that meets these requirements is represented with its basic and optional features as a block diagram in the attached figure. The invention is a process for the preparation of di-n-butene and alkyl tert-butyl ether in a coupled production from field butanes, in which (a) the n-butanes and iso-butanes contained are dehydrogenated. in the field butanes 1 in a dehydrogenation step 2, (b) in a dehydrogenation step 6 the n-butane 5 is dehydrogenated to a dehydrogenation mixture 7, the n-butene is oligomerized in the oligomerization step 10 to a mixture of oligomers 11 and di-n-butene 12 is separated from them, and (c) in dehydrogenation step 16, iso-butane 15 is dehydrogenated to a dehydrogenation mixture 7 containing n-butene and iso-butene in the step of etherification 19 it is transformed with an alkanol 20 to an alkyl tertiary butyl ether 21. A preferred diment of the process is characterized in that the butanes in field 1, before entering the separation step 4 2, in the hydrogenation step 2 they are subjected to hydrogenation conditions and the separation step 4 is subordinated to an isomerization step 3, by means of which the quantity ratio can be adjusted of n-butane to iso-butane according to the desired amount ratio of di-n-butene to alkyl tert-butyl ether. The process of the invention is characterized by a high flexibility, since, within the limits marked by the capacities of the di-n-butene installation and the installation of RTBE, the amounts of di-n-butene and RTBE can be varied. in a manner corresponding to the needs of the market. As field butanes, it is called the C fraction of the "wet" parts of the natural gas as well as the gases that accompany the oil, which are separated from the gases in liquid form by drying and cooling to approx. -30 ° -C. By distillation at low temperatures, butanes are obtained from them, whose composition varies depending on the place, but which, in general, contain approx. 30% isobutane and approx. 65% n-butane. Other components are, usually, approx. 2% hydrocarbons with less than 4 carbon atoms and approx. 3% hydrocarbons with more than 4 carbon atoms. The field butanes, without dissociation, can be used as a material in steam thermal decomposers or as additives for gasoline. They can be dissociated by fractional distillation in n-butane and iso-butane. Iso-butane is used, for example, in important amounts for the production of propylene oxide by co-oxidation of propylene and iso-butane, and as an alkylating agent, with which n-butene is alkylated, or else, iso- butene to iso-octane, which, due to its high octane rating, can be seen as an additive for gasoline. In contrast, n-butane found less significant applications. It serves, for example, as butane gas for heating purposes or, in comparatively small quantities, it is used for the preparation of polymers or copolymers or of anhydrous maleic acid by atmospheric oxidation. Before, n-butane, through the n-butene stage, was also dehydrogenated to 1,3-butadiene, but now this procedure is no longer profitable. As isobutane is the desired component of field butane, n-butane is isomerized on a large scale to isobutane (see, for example, R. A. Pogliano et al., Dehydrogenation-Based Ether Production, 1996 Petrochemical Review, DeWitt &; Company, Houston Texas, Butamer procedure * ', page 6; as well as S.T. Bakas, F. Nierlich et al, Production of Ethers from Field Butanes and Refinery Streams, AIChE Summer Meeting, 1990, San Diego, California, page 11). Therefore, it was not part of the technique's tendency to develop a process that takes advantage of n-butane as such or, even, transforms iso-butane into n-butane, to obtain more di-n-butene from them.

(A) Obtaining di-n-butene Field butane 1 is first separated in separation step 4 in n-butane 5 and iso-butane 15. This is best done in a column of good activity, in which it is separated by fractional distillation at a low temperature or, advantageously, under elevated pressure, suitably from 4 to 7 bar, the n-butane 5 of iso-butane 15, which, depending on the pressure, boils 10 to 20 SC less. Hydrocarbons of more than 4 carbon atoms remain as bottom residue, n-butane is sucked into the lateral flow and iso-butane goes first along with lighter ends. The n-butane 5 is taken to dehydrogenation step 6, which is itself well known. In this way a dehydrogenation mixture 7 containing n-butene is obtained. The processes usable for the dehydrogenation of light hydrocarbons have been described, for example, by G.C. Sturtevant et al., Oleflex -Selective Production of Light Olefins, 1988 UOP Technology Conference, as well as EP 0 149 698. Conveniently, dehydrogenation is carried out in the gas phase in solidly arranged or fluidized catalysts, for example chromium oxide (III). ) or, advantageously, in platinum catalysts with aluminum oxide or zeolites as carriers. The dehydrogenation generally takes place at temperatures of 400 to 800 ° C, advantageously 550 to 650 ° C. Work is usually carried out at atmospheric pressure or at slightly elevated pressure up to 3 bar. The residence time in the catalytic layer is, depending on the catalyst, the temperature and degree of reaction desired, in general between 1 and 60 minutes. The flow rate is correspondingly, usually 3, between 0.6 and 36 kg of n-butane per m of catalyst per hour. It is convenient to carry out the dehydrogenation only until the dehydrogenation mixture 7 remains unchanged approx. 50% of n-butane. At higher temperatures higher degrees of reaction could be achieved. However, decomposition reactions that lower the yield and, due to the deposit of coke, reduce the life of the dehydrogenation catalyst take place to a greater extent. The optimum combination of the reaction conditions leading to the desired degree of reaction, such as catalyst type, temperature and residence time, can be easily determined by orientation tests. The dehydrogenation mixture 7 usually contains 90 to 95% by weight of C4 hydrocarbons and furthermore hydrogen, as well as low and high boiling portions. Conveniently it is cleaned before oligomerization. In a first cleaning step (not shown in the figure) the C4 fraction and the high boiling portions are condensed. The condensate is distilled under pressure, with hydrocarbons of less than 4 dissolved carbon atoms condensed first. Of the bottom residue, the C4 hydrocarbons are obtained as the main product in another distillation and the comparatively small amount of hydrocarbons with more than 4 carbon atoms as the residue. The hydrocarbons C generally contain small amounts, for example 0.01 to 5% by volume, of 1,3-butadiene. It is advisable to remove this component, because even in clearly smaller amounts, it can damage the oligomerization catalyst. A suitable process is the selective hydrogenation 8, which, in addition, raises the part of the desired n-butene. A suitable procedure has been described, for example, by F. Nierlich et al. In Erdol & Kohle, Erdgas, Petrochemie, 1986, pages 73 et seq. It is carried out in the liquid phase with hydrogen completely dissolved in stoichiometric amounts. Suitable hydrogenation catalysts are, for example, nickel and particularly palladium on a carrier, for example 0.3% by weight of palladium on activated carbon or, preferably, on aluminum oxide. A small amount of carbon monoxide in the ppm range promotes the hydrogenation selectivity of the 1, 3-butadiene to monoolefin and causes the formation of polymers, contrary to the so-called "green oil", which deactivate the catalyst. The process works in general at room temperature or at an elevated temperature up to about 60 ° C and under high pressures, which move conveniently in the range of up to 20 bar. The 1,3-butadiene content in the dehydrogenation mixture is thus reduced to values of less than 1 ppm. It is also convenient, before the oligomerization step through another cleaning step 9, to bring the fraction C of the dehydrogenation mixture 7 almost completely liberated from 1,3-butadiene, to a molecular sieve in which other harmful substances for the oligomerization catalyst, which increases its life even more. Among these harmful substances are compounds of oxygen and sulfur. This cleaning procedure has been described by F. Nierlich et al. In EP-Bl 0 395 857. A molecular sieve with a pore diameter of 4 to 15 Angstrom, advantageously 7 to 13 Angstrom, is conveniently used. In some cases it is convenient for industrial reasons to run the dehydrogenation mixture consecutively by molecular sieves of various pore sizes. The process can be carried out in the gaseous, liquid or liquid-gas phase. According to the above, the pressure is generally 1 to 200 bar. It is conveniently worked at room temperature or at elevated temperatures until 2002C.

The chemical nature of molecular sieves is less important than their physical constitution, that is, in particular the size of the pores. It is therefore possible to use the most diverse molecular sieves, both crystalline and natural aluminum silicates, for example sheet silicates in layers, as well as synthetic molecular sieves, for example those with zeolite structure. Zeolites of type A, X and Y can be obtained, inter alia, from Bayer AG, Dow Chemical Co., Union Carbide Corporation, Laporte Industries Ltd. and Mobil Oil Co. Synthetic molecular sieves are also suitable for the process. which contain in addition to aluminum and silicon, also other atoms incorporated by exchange of cations, such as gallium, indium or lanthanum, as well as nickel, cobalt, copper, zinc or silver. Also suitable are zeolites in which, in addition to aluminum and silicon, other atoms, such as boron or phosphorus, were incorporated into the grid by mixed precipitation. As already mentioned, the selective hydrogenation step 8 and the cleaning step 9 with a molecular sieve are optional, advantageous steps for the process according to the invention. In principle, its sequence can be any, but the sequence shown in the figure is preferred. The dehydrogenation mixture 7, if appropriate treated in the manner described, is carried to the oligomerization stage 10, which is an essential part of the process according to the invention. The oligomerization is carried out in a manner known per se, for example, F. Nierlich has described in Oligomerization for Better Gasoline, Hydrocarbon Processing, 1992 (2), pages 45 et seq., Or F. Nierlich et al. In the document already mentioned EP-Bl 0 395 857. The process is generally carried out in the liquid phase and a homogeneous catalyst is used, for example, a system composed of octoate (II) of nickel, ethylaluminum chloride and a free fatty acid (DE-PS 28 55, 423), or one of the many known catalysts, solid or suspended in the oligomerization mixture, based on nickel and silicon, is preferably used. The catalysts often contain additional aluminum. Thus, DD-PS 160 037 discloses obtaining a precipitation catalyst containing nickel and aluminum on silicon oxide as a carrier material. Other usable catalysts are obtained by exchanging the positively charged particles located on the surface of the carrier materials, such as protons or sodium ions, by nickel ions. The above is achieved with the most diverse carrier materials, such as amorphous aluminum silicate (R. Espinoza et al., Appl. Kat., 31 (1987), pages 259-266; aluminum crystalline silicate (DE-PS 20 29 624); zeolites of the type ZSM (NL-PS 8 500 459); a zeolite X (DE-PS 23 47 235); X and Y zeolites (A. Barth et al., Z. Anorg, Allg. Chem. 521, (1985), pages 207-214); and a mordenite (EP-A 0 233 302). The oligomerization is conveniently carried out, according to the catalyst, at 20 to 2002 C and under pressures of 1 to 100 bar. The reaction time (or contact time) is generally 5 to 60 minutes. The parameters of the process, in particular the type of catalyst, the temperature and the contact time, are coordinated in such a way that the desired degree of oligomerization is achieved, that is, especially a dimerization. For this, of course, the reaction can not be carried out in its entire volume, but convenient transformations of 30 to 70% per shift are sought. Optimal combinations of the process parameters can be determined without difficulty by orientation tests. From the oligomerization mixture 11, the waste gases 14 are separated and fed back to the dehydrogenation step 6. If in the oligomerization step 10 a catalyst of the type of the aforementioned liquid catalysts was used, the waste gases 14 must be cleaned beforehand. to protect the dehydrogenation catalyst. The oligomerization mixture is first treated with water to extract the catalyst components. The separated waste gas is then dried with a suitable molecular sieve, also separating other secondary components. The variously unsaturated compounds, such as butines, are then removed by selective hydrogenation, for example with palladium catalysts, and, finally, the waste gas thus cleaned is brought to the dehydrogenation stage 6. These measures for the cleaning of the waste gas are not they are necessary if a solid oligomerization catalyst is used. From the remaining liquid phase of the oligomerization mixture 11, di-n-butene 12 and n-butene 13 trimer are separated by fractional distillation, ie, isomeric isdecenes, di-n-butene being the main product directly suitable for obtaining of nonanoles. The dodecenes 13 are a desired by-product. They can be hydroformylated, the hydroformylation products can be hydrogenated and the thus obtained tridecanols can be oxethylated, whereby valuable raw washing materials are obtained.

(B) Obtaining RTBE Isobutane 15 from separation step 4 is brought to dehydrogenation step 16 and there transformed into a dehydrogenation mixture 17 containing iso-butene. With regard to the process conditions, this dehydrogenation does not differ essentially from those of n-butane in the dehydrogenation step 6. Iso-butane can be dehydrogenated more easily than n-butane, so that, within the stated framework in the dehydrogenation stage 6, slightly milder conditions can be chosen. It is also convenient in this dehydrogenation to only look for a transformation of approximately 50%. The dehydrogenation mixture 17 contains, as described above for the dehydrogenation mixture 7, in addition to C4 hydrocarbons, hydrogen, as well as easier boiling components (which come in part from the field butanes and are partly formed with the dehydrogenation ), as well as higher boiling portions, and conveniently cleans before etherification. The above is carried out again in a first cleaning step (also not shown in the figure) that coincides with that described for cleaning the dehydrogenation mixture 7. The part of C4 thus obtained from the dehydrogenation mixture 17, is conveniently brought to through a selective hydrogenation step 18, in which dienes, such as propadiene and 1,3-butadiene, are selectively hydrogenated to monoolefins. The dienes are formed, for example, from propane, which was brought with the field butanes, from n-butane, which was not entirely separated from iso-butane in the separation step 4, or formed under the dehydrogenation conditions by isomerization and / or decomposition reactions. These dienes disturb, at least when realizing the residual gases 22, the reaction in the dehydrogenation step 16, less in the etherification step 19. Therefore, the selective hydrogenation step 18 can also be disposed after the etherification step. 19 in the waste gas flow 22, before or after the cleaning step 23. This arrangement allows, if necessary, reducing the reactor, since the volume of the waste gas flow 22 is, of course, smaller than that of the Dehydrogenation mixture 17. As regards the process conditions, reference is made to the explanations in relation to the selective hydrogenation step 8. The dehydrogenation mixture 17, optionally after the selective hydrogenation, is brought to the stage of etherification 19, wherein the iso-butene contained with an alkanol 20 is reacted in a manner known per se to obtain an RTBE (see, for example, Methyl-Tert-Butyl Ether, Ullmanns Enzyclopedia of I ndustrial Chemistry, Volume A 16, pages 543 et seq., VCH Verlagsgesellschaft, einheim). Of the alkanols those with 1 to 6 carbon atoms are preferred, for example, ethanol, isopropanol, isobutanol and, particularly, methanol. The reaction takes place in the liquid phase or in the liquid-gas phase, generally at a temperature of 50 to 90 ° C and under a pressure that is adjusted to the corresponding temperature. Conveniently, a slight stoichiometric excess of alkanol is used, with which the selectivity of the isobutene reaction is increased and its dimerization is reduced. As the catalyst, for example, an acid betonite or, advantageously, an acid ion exchanger with large pores is used. From the reaction mixture of the etherification step 19, the waste gas 22 and the eventual excessive alkanol of the RTBE 21 that formed was distilled off. In the case of MTBE, the waste gas 22 forms an azeotrope with methanol. This is washed with water and is separated in an aqueous phase from the waste gas 22, which is fed back to the dehydrogenation step 16, optionally via selective hydrogenation step 18 (then arranged correspondingly in the process sequence) and / or the cleaning step 23, the latter again conveniently a treatment with a molecular sieve, by means of which particularly impurities containing oxygen or sulfur are removed, which disturb the dehydrogenation catalyst. At least a part of the waste gas 22 can also be fed back to the separation step 4 (not shown in the figure), to avoid an enrichment of n-butane due to an inaccurate separation of n-butene and iso-butene in the separation step 4. The aqueous phase that is produced with the water washing is processed in methanol, which is fed back to the etherification, and in water, which is used again for washing.

(C) Variation of the amounts of di-n-butene and RTBE It is convenient to assign an isomerization step 3 to the separation stage 4, since in this way the proportion of the di-n-butene and RTBE amounts can be varied . The possibilities of variation are limited only by the capacities of the di-n-butene installation and that of RTBE. Considering investment costs, both facilities will rarely be so large that the total field butane flow available can only be processed in one facility while the other does not operate. Even so, the stage of isomerization 3 brings the possibility of reacting flexibly within the given limits, to the requirements of the market. If the field butanes contain unsaturated compounds, it is convenient to provide, in addition to the isomerization stage 3, a hydrogenation step 2, in which the unsaturated compounds are hydrogenated, as they disturb the isomerization. The hydrogenation is carried out in a manner known per se (see, for example, K. H. alter et al. In The Hüls Process for Selective Hydrogenation of Butadiene in Crude C4's, Develop in and Technical Application, DGKM-Tagung, Kassel, November 1993). Therefore, the liquid phase is conveniently worked and, depending on the catalyst, at room temperature or at an elevated temperature up to 90 ° C. and under a pressure of 4 to 20 bar, the partial pressure of the hydrogen being from 1 to 15 bar. The usual catalysts are used for the hydrogenation of olefins, for example, 0.3% palladium on aluminum oxide. The hydrogenated field butanes 1 are taken to separation step 4, where, as described, they are separated into n-butane 5 and iso-butane 15. If the n- / iso- ratio should be modified according to the respective need of both facilities, a part of the isomer present in excess in the isomerization stage 3 is removed. Alternative possibilities are indicated in the figure with dotted lines. In the isomerization step 3, the removed isomer is transformed into the other maximum isomer until equilibrium, which, depending on the temperature, is between 40 to 55% n-butane and 45 to 60% iso-butane. The isomerization of n- and iso-butane is a known reaction. In general, the gas phase is operated at a temperature of 150 to 230 ° C under a pressure of 14 to 30 bar and with a platinum catalyst on aluminum oxide as a carrier, whose selectivity can be further improved by providing it with a chlorine compounds, such as hydrocarbon tetrachlor. Advantageously, a small amount of hydrogen is added to counteract a dehydrogenation. The selectivity of the isomerization is high, the decomposition into smaller fractions only takes place in insignificant amounts (about 2%) (see, for example, HW Grote, Oil and Gas Journal, 56 (13), pages 573 et seq. (1958)). The isomerization mixture 24 must be separated in the isomers and is conveniently carried to the separation step 4 which already exists.

Claims (10)

NOVELTY OF THE INVENTION Having described the foregoing invention, the content of the following is claimed as property: CLAIMS

1. A process for obtaining di-n-butene and alkyl-butyl ethers in coupled production from field butanes, characterized in that (a) field butanes are separated in the separation step in n-butane and iso -butane, (b) in a dehydrogenation step the n-butane is dehydrogenated to a n-butene-containing dehydrogenation mixture, the n-butene is oligomerized in the oligomerization step to a mixture of oligomers and it is separated from it. -n-butene, and (c) in the dehydrogenation step, the isobutane is dehydrogenated to a dehydrogenation mixture containing n-butene and the iso-butene in the etherification step is transformed with an alkanol to an alkyl-ter. butyl ether.

2. A process according to claim 1, characterized in that the field butanes, before entering the separation stage, in the hydrogenation stage are subjected to hydrogenation conditions and the isomerization step is assigned to the separation step. , by which the amount ratio of n-butane and isobutane is adjusted according to the desired amount ratio of alkyl-butyl ether to di-n-butene.

3. A process according to claim 1 or 2, characterized in that between the dehydrogenation step and the oligomerization step, a selective hydrogenation step and / or a cleaning step is arranged in any sequence.

4. A process according to one of claims 1 to 3, characterized in that the residual gases are separated from the oligomerization mixture and, if necessary after cleaning, they are fed back to the dehydrogenation step.

5. A process according to one of claims 1 to 4, characterized in that a stage of selective hydrogenation is arranged between the dehydrogenation step and the etherification step.

6. A process according to one of claims 1 to 5, characterized in that the waste gases from the etherification step are fed back, via a cleaning step, to the dehydrogenation step.

7. A process according to one of claims 1 to 6, characterized in that, as the alcohol, ethanol, isopropanol, isobutanol or, particularly, methanol are used.

8. The use of di-n-butene obtained by a process according to one of claims 1 to 7, for the preparation of nonanoles by hydroformylation and hydrogenation of the hydroformylation product.

9. The use of the tri-n-butene (dodecene) obtained from the oligomerization mixture in a process according to one of claims 1 to 7, for the production by hydroformylation, hydrogenation of the product of the hydroformylation and oxyethylation of the product of the hydrogenation, of washing raw materials.

10. The use of the alkyl tertiary butyl ether obtained by a process according to one of claims 1 to 6, as an additive for gasoline.